/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.googlecode.jasperlib.internal.jasper.compiler.tagplugin;

/**
 * This interface allows the plugin author to make inqueries about the
 * properties of the current tag, and to use Jasper resources to generate direct
 * Java codes in place of tag handler invocations.
 */

public interface TagPluginContext {
    /**
     * @return true if the body of the tag is scriptless.
     */
    boolean isScriptless();

    /**
     * @param attribute
     *            Name of the attribute
     * @return true if the attribute is specified in the tag
     */
    boolean isAttributeSpecified(String attribute);

    /**
     * @return An unique temporary variable name that the plugin can use.
     */
    String getTemporaryVariableName();

    /**
     * Generate an import statement
     * 
     * @param s
     *            Name of the import class, '*' allowed.
     */
    void generateImport(String s);

    /**
     * Generate a declaration in the of the generated class. This can be used to
     * declare an innter class, a method, or a class variable.
     * 
     * @param id
     *            An unique ID identifying the declaration. It is not part of
     *            the declaration, and is used to ensure that the declaration
     *            will only appear once. If this method is invoked with the same
     *            id more than once in the translation unit, only the first
     *            declaration will be taken.
     * @param text
     *            The text of the declaration.
     **/
    void generateDeclaration(String id, String text);

    /**
     * Generate Java source codes
     */
    void generateJavaSource(String s);

    /**
     * @return true if the attribute is specified and its value is a
     *         translation-time constant.
     */
    boolean isConstantAttribute(String attribute);

    /**
     * @return A string that is the value of a constant attribute. Undefined if
     *         the attribute is not a (translation-time) constant. null if the
     *         attribute is not specified.
     */
    String getConstantAttribute(String attribute);

    /**
     * Generate codesto evaluate value of a attribute in the custom tag The
     * codes is a Java expression. NOTE: Currently cannot handle attributes that
     * are fragments.
     * 
     * @param attribute
     *            The specified attribute
     */
    void generateAttribute(String attribute);

    /**
     * Generate codes for the body of the custom tag
     */
    void generateBody();

    /**
     * Abandon optimization for this tag handler, and instruct Jasper to
     * generate the tag handler calls, as usual. Should be invoked if errors are
     * detected, or when the tag body is deemed too compilicated for
     * optimization.
     */
    void dontUseTagPlugin();

    /**
     * Get the PluginContext for the parent of this custom tag. NOTE: The
     * operations available for PluginContext so obtained is limited to
     * getPluginAttribute and setPluginAttribute, and queries (e.g.
     * isScriptless(). There should be no calls to generate*().
     * 
     * @return The pluginContext for the parent node. null if the parent is not
     *         a custom tag, or if the pluginConxt if not available (because
     *         useTagPlugin is false, e.g).
     */
    TagPluginContext getParentContext();

    /**
     * Associate the attribute with a value in the current tagplugin context.
     * The plugin attributes can be used for communication among tags that must
     * work together as a group. See <c:when> for an example.
     */
    void setPluginAttribute(String attr, Object value);

    /**
     * Get the value of an attribute in the current tagplugin context.
     */
    Object getPluginAttribute(String attr);
}
